An Introduction to Modular Waveform Digitizers

A digitizer is an electronic acquisition device that acquires analog waveforms, processes them through analog-to-digital converters (ADC’s) and sends the digitized sample to a buffer, which allows them to be saved before being processed by a computer. Historically, modern digitizers date from the 1950’s and 60’s when the need to rapidly acquire, store, and process multiple channels of data became evident. Most early digitizers were built on NIM (Nuclear Instrumentation Module) or CAMAC (Computer Automated Measurement And Control ) interface standards. These are standard bus and modular crate electronics standards for data acquisition and control used in nuclear and particle physics experiments. The creation of a standard instrument interface bus(GPIB/IEEE 488) in the 1970’s laid the foundation for multi instrument test and measurement systems. Concurrently the development of personal computers led to a number of standard computer interfaces such as PCI (Peripheral Component Interconnect ) and VMEbus (VersaModular Eurocard bus) providing a standard interface to interconnect peripheral devices within a computer. These computer buses were adapted to support modular instruments by the creation of a number of modular instrument interface buses such as PXI (PCI eXtensions for Instrumentation) and VXI (VME eXtensions for Instrumentation). The increasing need to reduce test time and data though put resulted in the development of the LXI (LAN eXtensions for Instrumentation) Standard for test system integration. So, all the elements for fast multichannel instrumentation systems are in place.